Shigellosis is the principal cause of clinical dysentery and a frequent cause of morbidity and mortality in children living in impoverished areas. Due to rapid appearance and spread of multiply antibiotic resistant strains and the lack of an available vaccine the morbidity and mortality from shigellosis is likely to increase without improved disease control measures. The proposed study will l) determine the community incidence rates of shigellosis and risk factors for the development of shigellosis in children under six years of age in the Peruvian Amazon; 2) characterize the relative importance of different routes of transmission by the genotyping of isolates from patients, family members, and household environmental sources; and 3) determine the diversity of isolates obtained in households of children with shigellosis and control households by genomic analysis, serotype, and antibiotic sensitivity profile. These data will contribute to an improved understanding of the epidemiology of shigellosis in an endemic area and therefore serve as the basis for the definition of the most highly effective interventions. The information on the serotypic diversity in the population as a whole and in households with children with dysentery will provide important data useful in vaccine development and establish this as a candidate site for future vaccine trials. The development and evaluation of a rapid highly discriminatory molecular typing system that is more readily applicable in less developed regions will facilitate future investigation in endemic areas. The collaborative team that is brought together to conduct the proposed study is an established international group of microbiologists, molecular geneticists, epidemiologists, and physicians with extensive experience training junior scientists in an international setting. This project will further strengthen these international connections in the process of the training of a junior clinician-scientist.